The present invention relates to the use of 4-chloro-5-[(4,5-dihydro-1H-imidazol-2-yl)-amino]-6-methoxy-2-methylpyrimi dine (moxonidine) and its physiologically acceptable acid-addition salts for the treatment and/or prophylaxis of disorders of thermogenesis and/or for the stimulation (increase) of thermogenesis in persons with abnormally low energy metabolism ("combustion") and/or in persons in whom thermogenesis is reduced during or following a weight-reducing diet, and to the manufacture of medicinal products suitable for this treatment and/or stimulation.